A man tossed a Molotov cocktail into a Lower East Side beauty salon on Sunday, injuring two people who were inside, police and sources said.

The frightening scene unfolded just before 5 p.m. at the Sa Sa II Beauty Salon, located at 129 Eldridge Street when the suspect was spotted by witnesses tossing the incendiary device into the business, according to police sources.

A 60-year-old woman suffered burns to her chest and a 46-year-old man suffered burns to his chest and arms. Both were taken to New York Presbyterian-Weill Cornell Medical Center in stable condition, police said.

The suspect fled the scene after the attack and no arrests were immediately reported.

Witnesses told The Post that the salon’s front door was locked at the time of the arson and those trapped inside were pounding on the door in a desperate bid to flee to safety as the building quickly filled with smoke.

“The whole store was filled with black smoke and we didn’t even realize that there was a fire or anything, but there was somebody pounding to get out and the door was locked,” Nick Gerrard, 30, who was having a drink next door, told The Post.

Gerrard said the smoke was so thick that he could only see the person’s fists banging on the glass door, and couldn’t make out his face.

Gerrard, of Brooklyn, tried to break the glass door with a stool, before he and another witness were finally able to pry it open a crack for the man stuck inside to escape.

He said the man whose “clothes were fully burned off” ran out of the building, followed by one or two people who were also inside. Then the flames grew.

“We saw the flames come up inside and there was black smoke billowing out the front door,” Gerrard said.

A manager from the business next door grabbed a fire extinguisher and began spraying the salon until the fire department showed up minutes later.

Firefighters got the flames under control at around 5:30 p.m., according to the FDNY.

Police and fire marshals are investigating the incident.